Airflow passage structure of manual pump of fluid-pumping apparatus

ABSTRACT

An airflow passage structure of manual pump of fluid-pumping apparatus includes a first control valve and a second control valve. The first and second control valves are movable between different positions to change flowing path of air so as to increase or decrease the air pressure in the chamber of a container of the fluid-pumping apparatus. In a relief operation mode, the air in the chamber is guided to go into a first compartment of the interior space of the manual pump and then go into a second compartment thereof to be exhausted into the atmosphere. On the other hand, in a pressurization operation mode, the communication between the chamber and the first compartment is interrupted and the air goes into the second compartment and then is pressurized and filled into the chamber to increase the pressure in the chamber.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a fluid-pumping technique, and more particularly to an airflow passage structure of manual pump of fluid-pumping apparatus.

2. Description of the Related Art

In the field of vehicle service, the fluid in the vehicle that needs to be replaced can be pumped out by means of a conventional pump device. The internal pressure of the container of the pump device for collecting the fluid is first decreased into a value lower than the atmospheric pressure to make the container in a negative pressure state. Under such circumstance, the fluid in the vehicle can be taken into the container via a pipeline and replaced with new fluid.

U.S. Pat. No. 7,367,366 discloses a typical pump device to provide a technique for changing the internal pressure of the container so as to take in or send out the fluid. However, in the above Patent, the pipeline as the airflow passage for guiding the air is arranged outside the container. Therefore, in practice, the pipeline is subject to damage or detachment due to incaution in use or operation. Accordingly, the technique provided by the above Patent is not optimal and needs to be improved.

SUMMARY OF THE INVENTION

It is therefore a primary object of the present invention to provide an airflow passage structure of manual pump of fluid-pumping apparatus. With the airflow passage structure, the internal pressure of the container of the fluid-pumping apparatus can be decreased or increased to take in or send out the fluid in accordance with actual requirements.

To achieve the above and other objects, the airflow passage structure of manual pump of fluid-pumping apparatus of the present invention includes: a container having a main body, a chamber with an open top end being formed in the main body, a cover section being disposed at the open end of the chamber to seal the chamber; a manual pump having a tubular body, a piston member being slidably disposed in the tubular body to partition an interior space of the tubular body into a first compartment and a second compartment, the piston member being reciprocally movable along an axis of the tubular body to make the capacities of the first and second compartments grow and decline, a pull stem being coaxially disposed in the tubular body, one end of the pull stem being connected with the piston member, the other end of the pull stem extending through the cover section to an outer side of the tubular body; a flow passage section including an in-stem flow passage formed in the pull stem and extending along an axis of the pull stem, an opening of the in-stem flow passage at one end of the pull stem communicating with the second compartment, the in-stem flow passage communicating with the atmosphere via an air outlet flow passage, a valve hole being formed in the cover section, one end of the valve hole communicating with the first compartment, an extension flow passage communicating the second compartment with the valve hole, the air being only permitted to one-way flow from the second compartment through the extension flow passage to the valve hole, a connection flow passage communicating the valve hole with the chamber; a first control valve movable between a first position and a second position, when positioned in the first position, the first control valve interrupting communication between the air outlet flow passage and the in-stem flow passage, when positioned in the second position, the first control valve permitting communication between the air outlet flow passage and the in-stem flow passage; and a second control valve movable between a pressurization position and a relief position, when positioned in the pressurization position, the connection flow passage communicating with the second compartment via the extension flow passage, when positioned in the relief position, the connection flow passage communicating with the first compartment via the valve hole.

In the above airflow passage structure of manual pump of fluid-pumping apparatus, the connection flow passage includes a first subsidiary connection flow passage and a second subsidiary connection flow passage. In the relief operation and pressurization operation of the chamber, the first and second subsidiary connection flow passages provide independent airflow paths. Accordingly, when the second control valve is positioned in the relief position, the first subsidiary connection flow passage communicates with the first compartment via the valve hole and the communication between the second subsidiary connection flow passage and the second compartment via the extension flow passage is interrupted. When the second control valve is positioned in the pressurization position, the communication between the first subsidiary connection flow passage and the first compartment via the valve hole is interrupted and the second subsidiary connection flow passage communicates with the second compartment via the extension flow passage. Accordingly, the air can one-way flow from the second compartment through the extension flow passage and the second subsidiary connection flow passage into the chamber.

The present invention can be best understood through the following description and accompanying drawings, wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective assembled view of a first preferred embodiment of the present invention;

FIG. 2 is a perspective exploded view of the first preferred embodiment of the present invention;

FIG. 3 is a sectional view of the first preferred embodiment of the present invention, showing that the chamber is being pressurized;

FIG. 4 is a sectional view of a part of the first preferred embodiment of the present invention, showing that the chamber is being pressurized;

FIG. 5 is a sectional view taken along line 5-5 of FIG. 4;

FIG. 6 is a sectional view of the first preferred embodiment of the present invention, showing that the chamber has been pressurized;

FIG. 7 is a sectional view of the first preferred embodiment of the present invention, showing that the chamber is being relieved;

FIG. 8 is a sectional view of a part of the first preferred embodiment of the present invention, showing that the chamber is being relieved;

FIG. 9 is a sectional view taken along line 9-9 of FIG. 8;

FIG. 10 is a sectional view of the first preferred embodiment of the present invention, showing that the chamber has been relieved;

FIG. 11 is a sectional view of a second preferred embodiment of the present invention, showing that the chamber is being pressurized;

FIG. 12 is a sectional view of a part of the second preferred embodiment of the present invention, showing that the chamber is being pressurized;

FIG. 13 is a sectional view taken along line 13-13 of FIG. 12;

FIG. 14 is a sectional view of the second preferred embodiment of the present invention, showing that the chamber has been pressurized;

FIG. 15 is a sectional view of the second preferred embodiment of the present invention, showing that the chamber is being relieved;

FIG. 16 is a sectional view of a part of the second preferred embodiment of the present invention, showing that the chamber is being relieved;

FIG. 17 is a sectional view taken along line 17-17 of FIG. 16; and

FIG. 18 is a sectional view of the second preferred embodiment of the present invention, showing that the chamber has been relieved.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Please refer to FIGS. 1 to 10. According to a first preferred embodiment, the airflow passage structure 10 of manual pump of fluid-pumping apparatus of the present invention includes a container 20, a manual pump 30, a flow passage section 40, a first control valve 50 and a second control valve 60.

The container 20 has a main body 21. A chamber 22 with an open top end is formed in the main body 21 to provide a certain capacity for containing the fluid taken in or to be sent out by the fluid-pumping apparatus. A cover section 23 is disposed at the open end of the chamber 22 to block the same. One side of the cover section 23 is formed with an opening 24 in communication with the chamber 22 and the atmosphere. A slide hole 25 is formed at a center of the cover section 23.

The manual pump 30 has a tubular body 31 received in the chamber 22 and coaxial with the slide hole 25. A top end of the tubular body 31 is connected with the cover section 23. A sealing cap 32 is fitted on a bottom end of the tubular body 31 to isolate the interior space of the tubular body 31 from the chamber 22. A piston member 33 is slidably disposed in the tubular body 31 to partition the interior space of the tubular body 31 into a first compartment 311 positioned above the piston member 33 and a second compartment 312 positioned under the piston member 33. Along with the slide movement of the piston member 33, the capacities of the first and second compartments 311, 312 grow and decline. A pull stem 34 is coaxially slidably fitted in the slide hole 25. A bottom end of the pull stem 34 is fixedly connected with the piston member 33. A top end of the pull stem 34 outward extends through the cover section 23 to upper side thereof. A pull handle 35 is perpendicularly fixedly connected to the top end of the pull stem 34.

The flow passage section 40 includes an in-stem flow passage 41 formed in the pull stem 34 and extending along the axis of the pull stem 34 between the top and bottom ends thereof. An opening of the in-stem flow passage 41 at the bottom end of the pull stem 34 communicates with the second compartment 312. A receiving hole 42 inward extends from one end of the pull handle 35, while a one-way air outlet flow passage 43 inward extends from the other end of the pull handle 35. The receiving hole 42 and the air outlet flow passage 43 communicate with the in-stem flow passage 41. A valve hole 44 is formed in the cover section 44. One end of the valve hole 44 communicates with the first compartment 311. A one-way extension flow passage 45 communicates the second compartment 312 with the valve hole 44. A connection flow passage 46 communicates the valve hole 44 with the chamber 22. An air inlet 47 communicates the valve hole 44 and the atmosphere.

To speak more specifically, one-way valves 431, 451 are respectively disposed in the air outlet flow passage 43 and the extension flow passage 45 to provide one-way flowing effect.

The first control valve 50 is disposed on the pull handle 23 and positioned in the junction between the air outlet flow passage 43 and the in-stem flow passage 41. The first control valve 50 is rotatable between a first position and a second position. When positioned in the first position, the first control valve 50 interrupts communication between the air outlet flow passage 43 and the in-stem flow passage 41. Reversely, when positioned in the second position, the first control valve 50 allows communication between the air outlet flow passage 43 and the in-stem flow passage 41.

To speak more specifically, the first control valve 50 has a first valve body 51 having a cylindrical form. One end of the first valve body 51 is coaxially rotatably fitted in the receiving hole 42. The endmost section of the end of the first valve body 51 is positioned in the junction between the air outlet flow passage 43 and the in-stem flow passage 41. A flow guide space 52 is formed at the endmost section of the end of the first valve body 51. Accordingly, when the first control valve 50 is positioned in the second position, the in-stem flow passage 41 communicates with the air outlet flow passage 43 through the flow guide space 52.

The second control valve 60 is fitted in a part of the valve hole 44. The second control valve 60 is at least such dimensioned that it can block both the extension flow passage 45 and an opening of the connection flow passage 46, which opening is connected with the valve hole 44. The second control valve 60 is movable between a pressurization position, a relief position and a closed position. When positioned in the pressurization position, the connection flow passage 46 communicates with the second compartment 312 via the extension flow passage 45. When positioned in the relief position, the connection flow passage 46 communicates with the first compartment 311 via the other part of the valve hole 44.

To speak more specifically, the second control valve 60 has a second valve body 61 having a cylindrical form. The second valve body 61 is coaxially rotatably fitted in a part of the valve hole 44. One end of the second valve body 61 extends out of the cover section 23 as a forced end for a user to operate. A pressurization flow passage 62 in the form of an elongated channel is formed on the circumference of the second valve body 61 and extends along an axis of the second valve body 61 by a certain length. A relief flow passage 63 in the form of a tunnel is formed in the second valve body 61 and inward axially extends from the other end of the second valve body 61 by a certain depth. In addition, a radial opening 631 is formed on the second valve body 61 in a position in alignment with the connection flow passage 46. The opening 631 is angularly spaced from the open side of the pressurization flow passage 62 by a certain angle.

According to the above arrangement, when the second control valve 60 is positioned in the pressurization position, the connection flow passage communicates with the extension flow passage 45 via the pressurization flow passage 63 and the relief flow passage 63 communicates the air inlet 47 with the other part of the valve hole 44. When positioned in the relief position, the connection flow passage 46 communicates with the other part of the valve hole 44 via the relief flow passage 63 and the communication between the air inlet 47 and the other part of the valve hole 44 is interrupted. When positioned in the closed position, the body of the second valve body 61 blocks the opening of the connection flow passage 46 so as to interrupt the communication between the connection flow passage 46 and the extension flow passage 45 as well as the communication between the connection flow passage 46 and the other part of the valve hole 44.

According to the airflow passage structure 10 of manual pump of fluid-pumping apparatus of the present invention, a user can use the fluid-pumping apparatus to take in fluid in a relief operation mode or send out fluid in a pressurization operation mode. The operations are respectively described as follows:

When a user desires to relieve the chamber 22 for taking external fluid into the chamber 22, the first control valve 50 is positioned in the second position and the second control valve 60 is positioned in the relief position. Under such circumstance, the user can force the pull handle 35 to drive the piston member 33 to reciprocally move. At this time, the air in the chamber 22 will one-way go from the first compartment 311 into the second compartment 312. Then the air goes through the in-stem flow passage 41 to the air outlet flow passage 43 and goes out from the air outlet flow passage 43 into the atmosphere. Accordingly, the air pressure in the chamber 22 is lowered to be smaller than the atmospheric pressure. In this case, under the atmospheric pressure, the external fluid is taken into the chamber 22 with lower pressure through an external pipeline in communication with the chamber 22 via the opening 24. Accordingly, the external fluid can be taken in.

When the user desires to pressurize the chamber 22 to forcedly send out the fluid contained in the chamber 22 through the external pipeline, the first control valve 50 is positioned in the first position and the second control valve 60 is positioned in the pressurization position. Under such circumstance, the atmosphere can go from the air inlet 47 through the other part of the valve hole 44 into the first compartment 311. Then, the user can force the pull handle 35 to make the piston member 33 reciprocally move. At this time, the air in the second compartment 312 will sequentially go through the extension flow passage 45, the pressurization flow passage 62 and the connection flow passage 46 into the chamber 22. In this case, the pressure in the chamber 22 is increased and the fluid is sent out of the chamber 22 through the external pipeline.

The pressurization and relief operations of the chamber 22 of the fluid-pumping apparatus not only can be performed by means of the manual pump, but also can be performed by means of a conventional pneumatic apparatus with a Venturi tube structure, which employs high-pressure air as power source. Therefore, when it is desired to perform the operations with the pneumatic apparatus 70, the flow passage section 40 must be blocked to cease its air guide effect. In this case, the second control valve 60 is positioned in the closed position to interrupt the communication between the chamber 22 and other spaces through the connection flow passage 46. Under such circumstance, the pressurization and relief operations of the chamber 22 can be performed by means of a conventional pneumatic apparatus.

Please now refer to FIGS. 11 to 18, which show a second preferred embodiment of the airflow passage structure 10′ of manual pump of fluid-pumping apparatus of the present invention. The second embodiment is substantially identical to the first embodiment in structure. The second embodiment is only different from the first embodiment in that the connection flow passage 46′ of the second embodiment includes a first subsidiary connection flow passage 461′ and a second subsidiary connection flow passage 462′ in communication with the chamber 22′ and the valve hole 44′ respectively. In addition, in the second embodiment, the one-way structure disposed in the extension flow passage of the first embodiment is removed, while a one-way structure is disposed in the second subsidiary connection flow passage 462′. That is, a one-way valve 463′ is disposed in the first subsidiary connection flow passage 461′ to restrict the air to only one-way flow out of the chamber 22′ for keeping the chamber 22′ in a relief state. A one-way valve 464′ is disposed in the second subsidiary connection flow passage 462′ to restrict the air to only one-way flow into the chamber 22′ for keeping the chamber 22′ in a pressurization state.

Moreover, in the second embodiment, when the second control valve 60′ is positioned in the pressurization position, the second subsidiary connection flow passage 462′ communicates with the extension flow passage 45′ via the pressurization flow passage 62′. On the other hand, when the second control valve 60′ is positioned in the relief position, the first subsidiary connection flow passage 461′ communicates with the other part of the valve hole 44′ via the relief flow passage 63′.

According to the above arrangement, the second embodiment of the airflow passage structure 10′ of manual pump of fluid-pumping apparatus of the present invention can be used in the same manner to achieve the same effect as the first embodiment. The second embodiment is advantageous over the first embodiment in that the one-way valves 463′, 464′ can more truly keep the chamber 22′ in the pressurization state or relief state.

The above embodiments are only used to illustrate the present invention, not intended to limit the scope thereof. Many modifications of the above embodiments can be made without departing from the spirit of the present invention. 

1. An airflow passage structure of manual pump of fluid-pumping apparatus, comprising: a container having a main body, a chamber with an open top end being formed in the main body, a cover section being disposed at the open end of the chamber to seal the chamber; a manual pump having a tubular body, a piston member being slidably disposed in the tubular body to partition an interior space of the tubular body into a first compartment and a second compartment, the piston member being reciprocally movable along an axis of the tubular body to make the capacities of the first and second compartments grow and decline, a pull stem being coaxially disposed in the tubular body, one end of the pull stem being connected with the piston member, the other end of the pull stem extending through the cover section to an outer side of the tubular body; a flow passage section including an in-stem flow passage formed in the pull stem and extending along an axis of the pull stem, an opening of the in-stem flow passage at one end of the pull stem communicating with the second compartment, the in-stem flow passage communicating with the atmosphere via an air outlet flow passage, a valve hole being formed in the cover section, one end of the valve hole communicating with the first compartment, an extension flow passage communicating the second compartment with the valve hole, the air being only permitted to one-way flow from the second compartment through the extension flow passage to the valve hole, a connection flow passage communicating the valve hole with the chamber; a first control valve movable between a first position and a second position, when positioned in the first position, the first control valve interrupting communication between the air outlet flow passage and the in-stem flow passage, when positioned in the second position, the first control valve permitting communication between the air outlet flow passage and the in-stem flow passage; and a second control valve movable between a pressurization position and a relief position, when positioned in the pressurization position, the connection flow passage communicating with the second compartment via the extension flow passage, when positioned in the relief position, the connection flow passage communicating with the first compartment via the valve hole.
 2. The airflow passage structure of manual pump of fluid-pumping apparatus as claimed in claim 1, wherein the flow passage section further includes a one-way valve disposed in the extension flow passage for restricting flowing direction of the air.
 3. The airflow passage structure of manual pump of fluid-pumping apparatus as claimed in claim 1, wherein the manual pump further includes a pull handle fixedly connected to the other end of the pull stem, the air outlet flow passage inward extending from one end of the pull handle in communication with the in-stem flow passage.
 4. The airflow passage structure of manual pump of fluid-pumping apparatus as claimed in claim 1, wherein the first control valve has a first valve body having a cylindrical form, the first valve body being movable between the first and second positions, a flow guide space being formed on the first valve body, when the first control valve is positioned in the second position, the air outlet flow passage communicating with the in-stem flow passage via the flow guide space.
 5. The airflow passage structure of manual pump of fluid-pumping apparatus as claimed in claim 4, wherein the manual pump further includes a pull handle fixedly connected to the other end of the pull stem, the air outlet flow passage inward extending from one end of the pull handle in communication with the in-stem flow passage, the first valve body being rotatably disposed in the pull handle.
 6. The airflow passage structure of manual pump of fluid-pumping apparatus as claimed in claim 1, wherein the valve hole is formed in the cover section and the second control valve is fitted in the valve hole.
 7. The airflow passage structure of manual pump of fluid-pumping apparatus as claimed in claim 6, wherein the second control valve has a second valve body having a cylindrical form, one end of the second valve body being coaxially fitted in a part of the valve hole, the second valve body being rotatable between the pressurization position and the relief position.
 8. The airflow passage structure of manual pump of fluid-pumping apparatus as claimed in claim 7, wherein the second control valve further has a pressurization flow passage in the form of a channel, the pressurization flow passage being formed on a circumference of the second valve body, a relief flow passage in the form of a tunnel being formed in the second valve body and inward axially extending from one end of the second valve body, a radial opening being formed on the second valve body in a position in alignment with the connection flow passage, whereby when the second control valve is positioned in the pressurization position, the connection flow passage communicates with the extension flow passage via the pressurization flow passage and when positioned in the relief position, the connection flow passage communicates with the other part of the valve hole via the relief flow passage.
 9. The airflow passage structure of manual pump of fluid-pumping apparatus as claimed in claim 1, wherein the second control valve is further movable to a closed position, when positioned in the closed position, the second valve body of the second control valve blocks both the connection flow passage and the extension flow passage.
 10. The airflow passage structure of manual pump of fluid-pumping apparatus as claimed in claim 9, wherein the second control valve has a second valve body having a cylindrical form, one end of the second valve body being coaxially fitted in a part of the valve hole, the second valve body being rotatable between the pressurization position, the relief position and the closed position, the second control valve further having a pressurization flow passage in the form of a channel, the pressurization flow passage being formed on a circumference of the second valve body, a relief flow passage in the form of a tunnel being formed in the second valve body and inward axially extending from one end of the second valve body, a radial opening being formed on the second valve body in a position in alignment with the connection flow passage, whereby when the second control valve is positioned in the pressurization position, the connection flow passage communicates with the extension flow passage via the pressurization flow passage and when positioned in the relief position, the connection flow passage communicates with the other part of the valve hole via the relief flow passage and when positioned in the closed position, the second valve body of the second control valve blocks both the connection flow passage and the extension flow passage.
 11. The airflow passage structure of manual pump of fluid-pumping apparatus as claimed in claim 1, wherein the connection flow passage includes a first subsidiary connection flow passage and a second subsidiary connection flow passage in communication with the valve hole and the chamber respectively, when the second control valve is positioned in the relief position, the second subsidiary connection flow passage being blocked and the first subsidiary connection flow passage communicating with the first compartment via the valve hole, when the second control valve is positioned in the pressurization position, the first subsidiary connection flow passage being blocked and the second subsidiary connection flow passage communicates with the second compartment via the extension flow passage, whereby the air can one-way flow from the second compartment through the extension flow passage and the second subsidiary connection flow passage into the chamber.
 12. The airflow passage structure of manual pump of fluid-pumping apparatus as claimed in claim 11, wherein the valve hole is formed in the cover section and the second control valve is fitted in the valve hole.
 13. The airflow passage structure of manual pump of fluid-pumping apparatus as claimed in claim 12, wherein the second control valve has a second valve body having a cylindrical form, one end of the second valve body being coaxially fitted in a part of the valve hole, the second valve body being rotatable between the pressurization position and the relief position.
 14. The airflow passage structure of manual pump of fluid-pumping apparatus as claimed in claim 13, wherein the second control valve further has a pressurization flow passage in the form of a channel, the pressurization flow passage being formed on a circumference of the second valve body, a relief flow passage in the form of a tunnel being formed in the second valve body and inward axially extending from one end of the second valve body, a radial opening being formed on the second valve body in a position in alignment with the connection flow passage, whereby when the second control valve is positioned in the pressurization position, the second subsidiary connection flow passage communicates with the extension flow passage via the pressurization flow passage and when positioned in the relief position, the first subsidiary connection flow passage communicates with the other part of the valve hole via the relief flow passage.
 15. The airflow passage structure of manual pump of fluid-pumping apparatus as claimed in claim 11, wherein the second control valve is further movable to a closed position, when positioned in the closed position, the second valve body of the second control valve blocks both the first and second subsidiary connection flow passages and the extension flow passage.
 16. The airflow passage structure of manual pump of fluid-pumping apparatus as claimed in claim 15, wherein the second control valve has a second valve body having a cylindrical form, one end of the second valve body being coaxially fitted in a part of the valve hole, the second valve body being rotatable between the pressurization position, the relief position and the closed position, the second control valve further having a pressurization flow passage in the form of a channel, the pressurization flow passage being formed on a circumference of the second valve body, a relief flow passage in the form of a tunnel being formed in the second valve body and inward axially extending from one end of the second valve body, a radial opening being formed on the second valve body in a position in alignment with the connection flow passage, whereby when the second control valve is positioned in the pressurization position, the second subsidiary connection flow passage communicates with the extension flow passage via the pressurization flow passage and when positioned in the relief position, the first subsidiary connection flow passage communicates with the other part of the valve hole via the relief flow passage and when positioned in the closed position, the second valve body of the second control valve blocks both the first and second subsidiary connection flow passages and the extension flow passage.
 17. The airflow passage structure of manual pump of fluid-pumping apparatus as claimed in claim 8, wherein the flow passage section further includes an air inlet formed on the cover section in communication with the atmosphere, when the second control valve is positioned in the pressurization position, the air inlet communicating with the other part of the valve hole via the relief flow passage, while when positioned in the relief position, the communication between the air inlet and the other part of the valve hole being interrupted by the second valve body.
 18. The airflow passage structure of manual pump of fluid-pumping apparatus as claimed in claim 10, wherein the flow passage section further includes an air inlet formed on the cover section in communication with the atmosphere, when the second control valve is positioned in the pressurization position, the air inlet communicating with the other part of the valve hole via the relief flow passage, while when positioned in the relief position, the communication between the air inlet and the other part of the valve hole being interrupted by the second valve body.
 19. The airflow passage structure of manual pump of fluid-pumping apparatus as claimed in claim 14, wherein the flow passage section further includes an air inlet formed on the cover section in communication with the atmosphere, when the second control valve is positioned in the pressurization position, the air inlet communicating with the other part of the valve hole via the relief flow passage, while when positioned in the relief position, the communication between the air inlet and the other part of the valve hole being interrupted by the second valve body.
 20. The airflow passage structure of manual pump of fluid-pumping apparatus as claimed in claim 16, wherein the flow passage section further includes an air inlet formed on the cover section in communication with the atmosphere, when the second control valve is positioned in the pressurization position, the air inlet communicating with the other part of the valve hole via the relief flow passage, while when positioned in the relief position, the communication between the air inlet and the other part of the valve hole being interrupted by the second valve body. 